Among the many pleasures of cities are those moments when you come upon some unexpected person or place or business that seems wholly out of time. Walking in Houston yesterday, along the commercial stretch of West Alabama not far from the Menil Collection, I had one of those epiphanies, when I found myself in front of the storefront of Key Maps. A map store? You don't see many of those around these days.

It has been there since 1957, when it was opened by James Rau, and it is now operated by his daughter, Jen Marie Rau, "He was a jack of all trades, master of none," she says. But he seemed to have a knack for mapping, and an ever expanding city was well suited to a local cartographic business. His Key Map of Houston was inspired by the box-grid system used in maps created by the Canadian Mounties, which run back and forth horizontally as they descend, windshield-wiper style. The maps have long been beloved by delivery men and cops, who can quickly call out a location by its Key Map coordinates.

"Oh my god, yes. They're always good," said Thomas Itabyi, a Houston cabbie for 32 years. He had been a regular user, but now that GPS is natively installed in his taxi's computerized meter display, he's abandoned his Key Map, albeit reluctantly. "We've got the GPS for everything," he said. "I hate it but if you can't beat it, you better join them."

Rau isn't convinced, and is quick to point out that digital cartographic systems are frequently inaccurate, as anyone who has tried to navigate with one can attest. That won't be a problem for Key Maps. Their new Harris County Atlas—the 52nd edition of that book—has more than 1,900 new streets.